A need exists to provide better organic electronic devices such as organic light emitting devices (OLEDs) including better materials used in the devices. In particular, better OLED devices and materials, including hole transporting materials, are needed. An OLED operation is based on injection, transport and recombination of two types of charge carriers: holes and electrons. It is important in an OLED device to control the injection and transport of these two types of carriers so as to enable the recombination to occur in the emissive layer where the luminescent species are located. The location where these species meet and recombine can dictate the efficiency and lifetime of the device.
In particular, a need exists for novel hole transporting materials with great properties such as solubility, thermal stability, and electronic energy levels such as HOMO and LUMO, so that the materials can be adapted for different applications and to function with different materials such as light emitting layers, photoactive layers, and electrodes. In particular, good solubility and intractability properties are important. The ability to formulate the system for a particular application and provide the required balance of properties are also important.
Additional background material can be found in, for example, (a) Charge carrier transporting molecular materials and their applications in devices, Shirota, et al., Chem. Rev., 2007, 107, 953-1010, (b) Organic electroluminescent diodes, Tang, et al., Appl. Phys. Lett. 1987, 51, 913-915. Hole transport is important for a variety of electronics applications.